1. Filtrates from B. coli, B. typhosus, or meningococci injected into the skin of guinea pigs do not produce visible inflammation. When these injections are followed by intravascular injections of the same material, hemorrhages do not occur in the skin.
2. Guinea pigs sensitized to horse serum react with redness and edema to 0.1 or 0.01 cc. of horse serum injected into the skin, and subsequent intravascular injection of typhoid filtrate does not produce hemorrhage at the site of the reaction to horse serum.
3. When guinea pigs are injected into the skin with diphtheria toxin and these injections are followed by intravascular injection of filtrates from B. typhosus, hemorrhage occurs in the skin at the site of the reaction to diphtheria toxin.
4. When silver nitrate is injected into the skin of guinea pigs, redness, edema, and necrosis follow, and in a few guinea pigs small areas of hemorrhage can also be noticed. About half of the guinea pigs that have received an intravascular injection of typhoid filtrate react with hemorrhage at the site of the injection of silver nitrate.